Between flights, commercial and military aircraft typically park at a terminal facility. When parked, the aircraft engines may be powered down. Electrical power that would otherwise be supplied by the aircraft engines may be supplied by an external source, such as a ground power cart or a generator associated with a sky-bridge. A ground power connector at the end of a power supply cable couples the external power source to the aircraft. Commercial and military aircraft typically have a fixed connector somewhere on the underside near the nose landing gear. Aircraft fixed connectors comprise a receptacle with male contact pins positioned therein. Ground power connectors comprises a plug with female sockets positioned therein, wherein the plug mates with the receptacle and the female sockets mate with the male contact pins.
The coupling between the ground power connector and the fixed connector is typically maintained by a physical engagement of the mating forces at both the plug/receptacle and pin/socket interfaces. The Engineering Society for Advancing Mobility Land Sea Air and Space (SAE) has promulgated an Aerospace Standard related to cable assemblies and attachable plugs for external electric power; (SAE AS7974). If the total mating forces are not sufficiently great to maintain the coupling between the aircraft fixed connector (receptacle) and the ground power connector (plug), gravitational forces will disconnect the ground power connector (plug) from the aircraft fixed connector (receptacle), and the ground power connector (plug) will drop to the ground and likely become damaged or worn. In addition to the potential for damage to the ground power connector (plug), it is undesirable for the ground power connector (plug) to prematurely disconnect from the aircraft fixed connector (receptacle), because a disconnect results in a loss of power supply to the aircraft. Electrical connectivity can also be affected my low mating forces due to low socket to pin wiping forces that will not adequately remove tarnish, oxides and corrosion form the mating surfaces which is equally undesirable.
A socket contact is a female contact designed to mate to a pin or male contact. It is preferentially connected to the “power” side of a circuit where the pin is preferentially connected to the “return,” “ground” or “load” side of the circuit. There is no industry standard for this preference. It is also important for each of the individual female sockets of the ground power connector (plug) to maintain physical engagement through coupling forces with each of the corresponding individual male pins of the aircraft fixed connector (receptacle). When physical engagement through coupling forces is not maintained between a pin and a socket, electrical arcing may generate excessive resistance leading to excessive heat and increased electrical resistance to the power supply. Electrical arcing and excessive heat may prematurely damage the pin or the socket.
In typical commercial and military terminal operations, ground power connectors are coupled/decoupled to/from several different aircraft each day. The simple action of inserting the ground power connector (plug) into an aircraft fixed connector (receptacle) in conventional plugs wears mating surfaces at both the plug/receptacle and pin/socket interfaces. Such wear may prevent sufficient mating forces to maintain physical engagement. Further, such wear at the pin/socket interface may lead to poor physical engagement so as to result in electrical arcing and excessive heat at one or more of the individual pin/socket interfaces.